This work is concerned with the investigation of the mechanisms by which genes effect processes of embryonic differentiation in mammals. Material for these studies is obtained from mutations available in our mutant mouse colony. Among the mutations studied are those which affect the earliest stages of embryonic differentiation into different cell types, the differentiation of elements of the kidney, of muscle cells, of the nervous system and of derivatives of the neural crest. The effects of mutant genes are studied on different levels i.e., those of organs, tissues, cells as well as the ultrastructural and the biochemical levels. Methods employed include those of genetics as well as experimental embryology, histochemistry, tissue culture, electrophoresis, electron microscopy and biochemistry. These studies of experimental systems serve as models for the elucidation of similar mechanisms of genetic control of growth and differentiation in man. BIBLIOGRAPHIC REFERENCES: Glutamine synthetase in newborn mice homozygous for lethal albino alleles. Developmental Biology 45: 369-371, 1975 (with M.B. Schiffman and M.H. Moscona.) Lipid deficiencies, leukocytosis, brittle skin - a lethal syndrome caused by a mutation, edematous (oed), in the mouse. Genetics 81: 525-536, 1975. (with M.B. Schiffman, M.L. Santorineou, S.E. Lewis and H.A. Turchin.)